This application claims the priority of European Patent Application No. 08 016 676.2, filed Sep. 23, 2008, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a man-machine interface (MMI) for pilot assistance during take-off and landing of an airborne vehicle (particularly a helicopter) in reduced external visibility or in restricted visual conditions. In dry, desert-like regions (for example Afghanistan), severe swirling of sand and dust occurs in virtually every off-base landing of helicopters. This is caused by the so-called down wash of the main rotor. The sand and dust swirling often leads to the pilot's partial or total loss of external visibility from the cockpit (so-called brown out) subjecting him or her to the danger of loss of spatial orientation, particularly with regard to the pitch and/or roll angle, as well as inadvertent lateral drift of the aircraft. A similar effect can occur when landing in snow. This effect is referred to as white out.
German patent document DE 10 2004 051 625 A1 discloses a helicopter landing aid specifically for brown out conditions in which a virtual 3D view of the surrounding area is displayed in the perspective of the pilot on a display during the brown out, with the virtual view being generated on the basis of 3D data accumulated during the landing approach, before the brown out started.
International patent document WO 2005/015333 A2 also describes a helicopter landing aid for brown-out conditions, which combines surrounding-area information and flight state data produced by means of different sensors for pilot assistance, and continuously updates this data by means of a helicopter data bus. In this case, both the surrounding-area information on the one hand and the flight state data, such as velocity, movement direction, drift direction and height above ground, on the other hand, are displayed on a joint display.
Characteristic variables and information which are necessary or helpful for the pilot for a landing process in brown-out conditions are:                a) the height above ground,        b) the attitude of the aircraft in space, or with respect to the ground,        c) the movement direction and velocity above ground,        d) the change in the velocity above ground,        e) the change in the height above ground,        f) the obstruction situation at the landing point,        g) the ground character of the landing or touch down point,        h) the distance to and relative direction of a landing or touch-down point which has previously been selected.        
One important consideration for a universal, operationally compatible brown-out MMI is that the characteristic variables and information mentioned above must be passed to the pilot or pilots in an intuitive manner. On the other hand, particularly in the case of military helicopters, the pilot is provided with a large amount of information in the form of bars and columns of numbers. In extremely stressful situations, such as during a brown out, where the important factor is to react very precisely and very quickly to a changing flight situation, this may possibly lead to misinterpretations or even confusion by the pilot. For this reason, every display of the characteristic variables and information mentioned above must be presented in a form which is intuitive, and minimizes the stress on the pilot in this critical landing phase.
One object of the invention is to provide and improve man-machine interface for pilots such that, in the case of a brown-out or white-out landing, he or she is provided with optimized intuitive assistance for three-dimensional orientation, thus allowing a safe landing even and in particular in these extreme situations.
This and other objects and advantages are achieved by the man-machine interface according to the invention, in which a virtual scenario is presented, from the perspective of a virtual observer who is located behind the airborne vehicle and is in the same flight attitude as the airborne vehicle itself. This virtual scenario has the following components:                a base plane which symbolizes an idealized ground surface, calculated from the instantaneous value of the altitude above ground and the instantaneous flight attitude data. The base plane is bounded by an artificial horizon and is continuously updated with the instantaneous flying state data and the instantaneous height above ground.        a symbol for the airborne vehicle, whose position and attitude relative to the base plane represents the actual instantaneous flight attitude and the height of the airborne vehicle above ground (AGL).        
This display in particular makes it considerably easier for the pilot to control the flight attitude, with regard to pitch and roll, while at the same time providing him with an impression of the height above ground.
In further advantageous embodiments, additional displays can be projected onto the base plane, or onto a plane parallel to it:                a drift vector on or above the base plane, in order to indicate the instantaneous velocity and movement direction over ground;        an AGL indicator for visualization of the instantaneous altitude above ground;        a shadow of the airborne vehicle (on the basis of the current time of day or a fixed virtual light source) for additional visualization of the instantaneous height above ground;        a danger sector on or above the base plane for visualization of stationary or moving obstructions within the safety area of the landing zone; and        an intended landing or touch-down point which was chosen before the start of the brown out by a numerical position input or by means of a helmet-mounted sight, flight attitude data or a digital trigger and which is displayed continuously and in an accurate position on the base plane. In one particularly advantageous embodiment, the 3D data relating to the landing zone can also be included in the calculation of the landing point or touch-down point.        
The pilot is therefore provided with all the important flight, obstruction and terrain information within the landing zone, in a concentrated form, and he need not divert his attention away from the various displays or screens.
The impression of the instantaneous altitude can be further enhanced by continuously displaying a vertical from the airborne vehicle to the base plane.
In a further embodiment, the base plane has superimposed on it a three-dimensional display of the actual topographical terrain surface (in particular with respect to the conditions in front of, at the side of and under the airborne vehicle), on the basis of high-resolution 3D data.
The display according to the invention can prevent the pilot's loss of spatial orientation in the event of a brown out, and also allow assessment of the desired landing point or touch-down point. The flight attitude, height above ground and, furthermore, instantaneous drift rate and direction as well are in a concentrated form, in a manner which can be understood intuitively by the pilot. The pilot is presented with a universal, operationally compatible aid for helicopter landings, especially in brown-out conditions.
The MMI according to the invention is based on the use of a plurality of sensors (flight attitude and navigation system, one or more radar altimeters and/or laser altimeters) as a basic configuration, as well as additional laser-based ladar systems, video and FLIR cameras and/or dust-penetrating radar systems, as well as digital 3D terrain and obstruction databases as an option.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.